1. Field of the Invention
The present invention relates to a color selecting member in which a damper line for preventing vibration is provided in a tensioned state, a method of preventing vibration of the color selecting member, and a cathode ray tube having such a color selecting member.
2. Description of the Related Art
In a cathode ray tube, a color selecting member is provided for selecting an electron beam emitted from an electron gun, irradiating the selected electron beams only on phosphors of red, blue and green, respectively, and for projecting a video image according to each color onto a fluorescent screen.
FIG. 1 shows an example of the structure of a conventional color selecting member. The color selecting member 11 is what is called an aperture grille and is provided between a pair of frame members 13 under predetermined tension. A pair of arm members 12 are provided across both ends of the pair of frame members 13.
The color selecting member 11 is constructed by a metal thin plate and has: a number of striped apertures 14 which are arranged at a predetermined pitch and through which an electron beam passes; and linear electrodes 15 each of which has a string structure and is provided between neighboring apertures 14. The color selecting member 11 performs color selecting according to an incident angle of an electron beam entering the apertures 14.
In such a color selecting member 11, it is necessary to prevent occurrence of resonance due to vibration from the outside such as vibration caused by sound from a speaker, vibration caused during transportation between facilities at the time of manufacture of a fluorescent screen, and the like. Hitherto, the color selecting member 11 is therefore provided with two damper lines 16 constructed by thin metal lines which are in contact with the surface of the color selecting member 11 and are orthogonal to the linear electrodes 15 and apertures 14. Both ends of each of the damper lines 16 are attached to damper springs 17 provided for the arm members 12 under predetermined tension.
In the cathode ray tube using the conventional color selecting member 11, however, electron beams emitted from the electron gun are interrupted by the damper lines 16 which extend across the apertures 14 of the color selecting member 11. It causes a problem such that the electron beams do not hit the phosphors on the fluorescent screen sufficiently, a shadow of each of the damper lines 16 is cast on a video screen and, as a result, the quality of the video image deteriorates.
It can be considered that the shadow of the damper line 16 on the video screen is made inconspicuous by reducing the diameter of the damper line 16. In this case, however, since the strength at break of the damper line 16 deteriorates, the tension to press the surface of the color selecting member 11 has to be weakened. As a result, a problem lowering the effect of attenuating the vibration of the color selecting member 11 occurs.
Meanwhile, in recent years, in order to enlarge the screen while reducing the depth, a multiple electron gun type cathode ray tube having a plurality of electron guns has been developed. In such a multiple electron gun type cathode ray tube, as the screen becomes larger, the shadow of the damper line cast on the video screen becomes larger and more conspicuous.
The present invention was achieved in consideration of the problems with the aim of providing a color selecting member in which a shadow of a damper line cast on a video screen is made inconspicuous or the occurrence of a shadow is suppressed and yet whose vibration can be effectively prevented in a cathode ray tube having a plurality of electron guns, a method of preventing the vibration of the color selecting member, and a cathode ray tube having such a color selecting member.
A color selecting member according to the invention is used for a cathode ray tube having a plurality of electron guns and has a construction that a damper line for preventing vibration is provided in a tensioned state in a position opposite to an area on a fluorescent screen, which is irradiated with both electron beams emitted from neighboring electron guns. More specifically, when the color selecting member is used for a cathode ray tube in which electron beams emitted from neighboring electron guns cross each other before passing through a plurality of apertures, the damper line is provided in a tensioned state in an area through which both of the electron beams pass. When the color selecting member is used for a cathode ray tube in which electron beams emitted from neighboring electron guns cross each other after passing through the plurality of apertures, the damper line is provided in a tensioned state in an area through which both of the electron beams do not pass.
In a method of preventing vibration of a color selecting member according to the invention, a damper line is selectively provided in a tensioned state in a position opposite to an area on the fluorescent screen, the area being irradiated with both of the electron beams emitted from the neighboring electron guns, in accordance with whether the electron beams emitted from the neighboring electron guns cross each other before or after passing through the plurality of apertures.
Further, the cathode ray tube according to the invention has a color selecting member as described above.
In the color selecting member, the method of preventing vibration of the color selecting member, and the cathode ray tube according to the invention, since the damper line is provided in a tensioned state on an area of the color selecting member, which is opposite to the area on the fluorescent screen irradiated with both electron beams emitted from neighboring electron guns, a shadow of the damper line cast on the fluorescent screen can be lightened or prevented. That is, in the cathode ray tube in which the electron beams emitted from the neighboring electron guns cross each other before passing through the plurality of apertures, even when a shadow of the damper line is cast on the fluorescent screen by one of the electron beams, the other electron beam falls on the shadow, thereby lightening the shadow. In the cathode ray tube in which the electron beams emitted from the neighboring electron guns cross each other after passing through the plurality of apertures, neither of the electron beams hits the damper line, so that the shadow of the damper line is not cast.
Other and further objects, features and advantages of the invention will appear more fully from the following description.